EP0106547B1 - Verfahren zur Herstellung eines Oxyd-Einkristalls - Google Patents

Verfahren zur Herstellung eines Oxyd-Einkristalls Download PDF

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Publication number
EP0106547B1
EP0106547B1 EP83305489A EP83305489A EP0106547B1 EP 0106547 B1 EP0106547 B1 EP 0106547B1 EP 83305489 A EP83305489 A EP 83305489A EP 83305489 A EP83305489 A EP 83305489A EP 0106547 B1 EP0106547 B1 EP 0106547B1
Authority
EP
European Patent Office
Prior art keywords
crystal
ferrite
growing
oxygen
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP83305489A
Other languages
English (en)
French (fr)
Other versions
EP0106547A3 (en
EP0106547A2 (de
Inventor
Mineo Yorizumi
Hidemasa Tamura
Yoshimi Makino
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sony Corp
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Sony Corp
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Filing date
Publication date
Application filed by Sony Corp filed Critical Sony Corp
Publication of EP0106547A2 publication Critical patent/EP0106547A2/de
Publication of EP0106547A3 publication Critical patent/EP0106547A3/en
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Publication of EP0106547B1 publication Critical patent/EP0106547B1/de
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B13/00—Single-crystal growth by zone-melting; Refining by zone-melting
    • C30B13/16—Heating of the molten zone
    • C30B13/22—Heating of the molten zone by irradiation or electric discharge
    • C30B13/24—Heating of the molten zone by irradiation or electric discharge using electromagnetic waves
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B13/00—Single-crystal growth by zone-melting; Refining by zone-melting
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C30B29/22—Complex oxides
    • C30B29/26—Complex oxides with formula BMe2O4, wherein B is Mg, Ni, Co, Al, Zn, or Cd and Me is Fe, Ga, Sc, Cr, Co, or Al

Definitions

  • the invention relates to a method of manufacturing an oxide single crystal and, more specifically, to a method of growing a single crystal of magnetic oxide material such as ferrite by way of a floating zone process through direct heating.
  • the floating zone process has heretofor been employed for growing a single crystal and the process has various merits such as avoiding the requirement for a melt crucible, the capability of optionally selecting the crystallographic direction of a grown crystal, homogenizing of the grown crystal by zone levelling and providing a high working efficiency.
  • Ferrite is a non-stoichiometric compound in which the ratio of the constituent elements cannot be expressed by simple integers and the logarithmic value of the equilibrium oxygen pressure for ferrite in a certain composition varies in proportion to the reciprocal of the temperature for the crystal. As can be seen from the equilibrium oxygen pressure line which is discontinuous at the melting point of ferrite, ferrite releases oxygen gas upon melting.
  • Patent Specification EP-A-0 018 111 discloses a method of growing ferrite single crystals by melting a starting material in an atmosphere having a total pressure of at least 1 atmosphere and an oxygen partial pressure higher than that in air wherein the crystal is heated by supporting it preferably on a susceptor and inductively heating the susceptor.
  • Patent Specification DE-A-2 100 584 discloses a method of producing orthoferrite single crystals by the floating zone-melting method from a polycrystalline body in air or an oxygen rich atmosphere having a pressure in the range 1 to 10 atmospheres.
  • the concentration of the oxygen gas in the atmospheric gas is excessively high, the oxygen gas released upon melting of the ferrite remains on the surface of a melt-zone as gas bubbles, which disturb the solid-liquid interface or are incorporated in the crystal and seriously degrade the crystallinity.
  • the temperature of the grown crystal is lowered in the course of growing due to the steep temperature gradient inherent in the floating zone process. Consequently, the oxygen gas pressure in the growing atmosphere goes higher than the equilibrium oxygen pressure as the temperature for the crystal decreases in the course of the growing even if the values for these pressures were equal upon melting of the ferrite. This causes oxidation on the surface of the crystal to deposit a-Fe 2 0 3 and induce cracks in the crystal.
  • a method of manufacturing an oxide single crystal byway of the floating zone method through direct heating characterized in that heating is effected in an atmosphere containing 10% to 40% oxygen, the temperature of the crystal (5) during growing is maintained above 1000°C, and the grown crystal (5) is gradually cooled after the completion of growing and after replacing the atmosphere with an inert gas containing less than 10- S atmospheres MPa of oxygen.
  • the generation of gas bubbles during melting can be suppressed to stabilize a melt-zone and oxidation on the surface of the grown crystal can be prevented.
  • the crystal is ferrite, preferably Mn-Zn ferrite.
  • the entire pressure of the gaseous mixture is preferably from 10 5 to 10 7 Pa (1 to 100 atm) and the temperature of the crystal during growing is preferably maintained above 1200°C.
  • the apparatus 1 comprises an infrared heating chamber 3 having an inner wall surface 2 formed as a rotational ellipsoidally curved plane.
  • the inner wall surface 2 of the infrared heating chamber 3 is formed as a rotational elliptic mirror by gold plating, and a halogen lamp 4 is situated as an infrared source at one focal point E 1 of the rotational ellipse.
  • a shaft 6 capable of vertical and rotational movements having a seed crystal 5 made of a single ferrite crystal at the upper end thereof and a shaft 11 also capable of vertical and rotational movements having a polycrystalline rod 7 as a starting material at the lower end thereof, such that both of the shafts pass through the other focal point E 2 of the rotational ellipse.
  • infrared rays 12 emitted from the halogen lamp 4 are reflected on the inner wall surface 2 and concentrated at the other focal point E 2 locally to heat the polycrystalline ferrite rod 7 situated at the focal point E 2 .
  • the thus heated polycrystalline ferrite rod 7 is melted from the lower end and successiveively grown into a single ferrite crystal 13, which is gradually cooled while being transferred downwardly within a cylindrical sub-heater 14 disposed below the focal point E 2 .
  • the sub-heater 14 is secured at its lower end to an aluminum cylinder 15 which receives the shaft 6.
  • the cylinder 15 is connected at its lower end to a feed pipe 16 for introducing an atmospheric gas as described below.
  • a quartz tube 17 is disposed substantially vertically around the shaft 11, the sub-heater 14 and the cylinder 15, and the inside of the quartz tube 17 is filled with a predetermined atmospheric gas for the crystal growth.
  • the atmospheric gas is supplied from the feed pipe 16 at the lower end of the apparatus and discharged through an exhaust pipe 21 at the upper end of the apparatus.
  • the growing state of the crystal is projected by way of a lens 22 and displayed on a screen 23.
  • the polycrystalline ferrite rod 7 and the seed crystal 5 are at first situated fixedly in close contact with each other at the position of the focal point E 2 . Then, a gaseous mixture 24 containing oxygen at a predetermined concentration is introduced through the feed pipe 16 into the quartz tube 17 to establish a predetermined pressure within the quartz tube 17. Then, the polycrystalline ferrite rod 7 and the seed crystal 5 are rotated by respective motors 27, 31 in opposite directions to each other as shown in Figure 3, and the entire connection area between both of them is rendered to the state of a molten crystal 25 under infrared heating by the halogen lamp 4 to form a melt-zone 26.
  • the polycrystalline ferrite rod 7 By lowering both the polycrystalline ferrite rod 7 and the seed crystal 5 while rotating them by the motors 27 and 31, the polycrystalline ferrite rod 7 is continuously melted from its lower end upwards and made into a single ferrite crystal by gradual cooling in the sub-heater 14.
  • Figure 6 shows a relationship between the equilibrium oxygen pressure P0 2 and the crystal temperature T for Mn-Zn ferrite in the floating zone process.
  • a solid line a represents the equilibrium oxygen pressure line for ferrite having a composition consisting of 50 mol% Fe 2 0 3 , 20 mol% ZnO and 30 mol% MnO
  • a solid line b represents the equilibrium oxygen pressure line for ferrite having a composition consisting of 55 mol% Fe 2 0 3 , 20 mol% ZnO and 25 mol% MnO.
  • a dotted line c represents an upper limit for the region where a stable spinel phase, i.e., composed only of ferrite is present, while a dotted line d represents the lower limit therefor.
  • the foregoing defects have been overcome in the method according to the present embodiment by introducing a gaseous mixture through the pipe 16 of an oxygen gas and a chemically inert gas (for example Ar) as an atmospheric gas during growing of a single crystal and by setting the concentration of the oxygen in the gaseous mixture to be 10% to 40% as expressed by the oxygen partial pressure.
  • a gaseous mixture through the pipe 16 of an oxygen gas and a chemically inert gas (for example Ar) as an atmospheric gas during growing of a single crystal and by setting the concentration of the oxygen in the gaseous mixture to be 10% to 40% as expressed by the oxygen partial pressure.
  • a chemically inert gas for example Ar
  • the pressure for the growing atmosphere that is, the total pressure of oxygen pressure and inert gas pressure is, desirably, in a range from an ambient pressure up to 100 atm.
  • a powderous mixture having a ferrite composition consisting of 53 mol% Fe 2 0 3 , 20 mol% ZnO and 27 mol% MnO was pressed under a pressure of 1 t/cm 2. Then, the pressed product was moulded into a cylinder of 20 ⁇ x100 mm length and sintered at 1400°C for 5 hours in an oxygen gas. Then, the starting rod was closely contacted with and secured to a Mn-Zn ferrite seed crystal within the quartz tube, and the seed crystal was melted through infrared direct heating to form a melt-zone between the starting rod and the seed crystal under the entire pressure of 10 atm within the quartz tube.
  • the starting rod and the seed crystal were rotated each at 30 rpm in directions opposite to each other and both of them were moved downwardly at a rate of 20 mm/hr to grow a single crystal.
  • the molten state of the ferrite under various atmospheric oxygen pressures was as below: wherein the symbol "x" represents the generation of gas bubbles in the melt-zone thus failing to obtain single crystal at high quality, the symbol “0” represents the possible remaining of gas bubbles in the single crystal or reduction of the oxygen ratio in the single crystal and the symbol "0" represents the formation of a smooth melt-zone enabling a single crystal of high quality to be obtained.
  • a smooth melt-zone can be prepared thereby to obtain a single crystal stably of high quality by selecting the composition of the atmosphere during growing. Further, since the entire pressure is kept unchanged even if the oxygen pressure is decreased, an easily volatilizing substance such as Zn, if present in the composition of the grown crystal, can be suppressed from volatilization. Furthermore, oxidation on the surface of the crystal can be suppressed thereby to prevent the deposition of a-Fe 2 0 3 on the surface of the crystal during growing.
  • the temperature for the crystal is always maintained above 1000°C, preferably, above 1200°C in the course of growing the single crystal, as well as that the thus grown crystal is gradually cooled to a room temperature after the completion of the growing and after replacing the atmosphere with a chemically inert gas such as Ar or N 2 containing such a trace amount of oxygen as: PO 2 ⁇ 10 -5 atm., which will be detailed hereinafter.
  • the replacement of the atmosphere is carried out by discharging the gaseous mixture from the exhaust pipe 21 while supplying the inert gas as described above from the feed pipe 16.
  • the limiting line is flat below about 700°C, because the reaction rate is retarded due to the low temperature, at which the effect of an oxidizing atmosphere is negligible.
  • the points for the equilibrium oxygen pressures: 10- 3 , 10- 4 , 10- 5 , 10- 6 atm at 750°C were determined by mirror- finishing the slices of the ferrite, maintaining the slices at 750°C for one hour and, thereafter, observing the a-Fe 2 0 3 at the surface of them.
  • the crystal in order to obtain a crack-free crystal, the crystal must be maintained at a temperature higher than the limiting line e, that is, above 1000°C, (preferably above 1200°C) during the growing stage and gradually cooled after replacing the atmosphere with an inert gas containing less than 10- 5 atm of oxygen during the cooling stage.
  • the inert gas to be mixed as the atmospheric gas during growing may consist of one or more inert gases.
  • a gaseous mixture comprising an oxygen gas of 10% to 40% concentration and an inert gas is used as the atmospheric gas during growing of a crystal, it is possible to obtain a crystal of high quality by suppressing the generation of gas bubbles upon melting to stabilize the melt-zone and further prevent the oxidation on the surface of the grown crystal by the reduction of the oxygen pressure.
  • the temperature for the crystal during growing is set to above 1000°C and, thereafter, the grown crystal is gradually cooled after replacing the atmospheric gas at least partially with an inert gas, no foreign substance such as hematite is produced on the surface of the crystal, that is, surface oxidation can be prevented thereby effectively to avoid the generation of cracks.
  • Atmosphere throughout the specification is meant a pressure equal to 100,000 Pascals.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Soft Magnetic Materials (AREA)

Claims (5)

1. Verfahren zur Herstellung eines Oxyd-Einkristalls auf dem Weg des tiegelfreien Zonenziehens durch Direkterwärmung, dadurch gekennzeichnet,
-daß die Erwärmung in einer Atmosphäre, die 10 Mol-% bis 40 Mol-% Sauerstoff enthält, bewerkstelligt wird,
-die Temperatur des Kristalls (5) während des Wachstums über 1000°C gehalten wird, und
-der gewachsene Kristall (5) nach Vervollständigung des Wachstums und nach Austausch der Atmosphäre durch ein Inertgas, das weniger als 10-5 at (1 Pa) Sauerstoff enthält, schrittweise abgekühlt wird.
2. Verfahren gemäß Anspruch 1, dadurch gekennzeichnet, daß der Kristall (5) Ferrit ist.
3. Verfahren gemäß Anspruch 2, dadurch gekennzeichnet, daß das Ferrit ein Mn-Zn-Ferrit ist.
4. Verfahren gemäß Anspruch 1, dadurch gekennzeichnet, daß der Gesamtdruck der Gasmischung von 1 bis 100 at (105 bis 107 Pa) ist.
5. Verfahren gemäß Anspruch 1, dadurch gekennzeichnet, daß die Temperatur des Kristalls (5) während des Wachstums oberhalb von 1200°C gehalten wird.
EP83305489A 1982-09-18 1983-09-19 Verfahren zur Herstellung eines Oxyd-Einkristalls Expired EP0106547B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP57162783A JPS5954690A (ja) 1982-09-18 1982-09-18 結晶育成方法
JP162783/82 1982-09-18

Publications (3)

Publication Number Publication Date
EP0106547A2 EP0106547A2 (de) 1984-04-25
EP0106547A3 EP0106547A3 (en) 1986-01-22
EP0106547B1 true EP0106547B1 (de) 1989-05-17

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EP83305489A Expired EP0106547B1 (de) 1982-09-18 1983-09-19 Verfahren zur Herstellung eines Oxyd-Einkristalls

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JP (1) JPS5954690A (de)
DE (1) DE3379871D1 (de)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101910473A (zh) * 2007-12-25 2010-12-08 株式会社水晶系统 浮区熔化装置

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL6506497A (de) * 1964-05-23 1965-07-26
FR1459875A (fr) * 1965-08-11 1966-06-17 Centre Nat Rech Scient Perfectionnements apportés aux moyens pour ajuster à une valeur prédéterminée au cours d'un cycle thermique la teneur d'un corps en l'un de ses constituants volatils
GB1294272A (en) * 1970-08-05 1972-10-25 Nippon Electric Co Method of making orthoferrite single crystals
JPS55130898A (en) * 1979-04-02 1980-10-11 Hitachi Ltd Preparation of ferrite single crystal

Also Published As

Publication number Publication date
DE3379871D1 (en) 1989-06-22
EP0106547A3 (en) 1986-01-22
EP0106547A2 (de) 1984-04-25
JPS5954690A (ja) 1984-03-29

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